Boris Johnson was warned about granting a peerage to his close friend Evgeny Lebedev two years ago by British intelligence.
According to a report in the Sunday Times, the head of MI6 held security concerns over the Russian oligarch (who, the newspaper says, has previously defended Russia's Vladimir Putin and expressed doubt over the murder of a Kremlin critic in London) as long as a decade ago.
Opposition leader Sir Keir Starmer expressed alarm over the article’s allegations and said he had written to the House of Lords Appointment Commission chair Lord Brew to raise concerns over the Prime Minister’s decision to grant Lord Lebedev a peerage.
In a statement, the Labour leader questioned the judgement of Mr Johnson for nominating to the House of Lords "someone who has promoted the worst conspiracy theories and defences of Vladimir Putin".
Sir Keir, the former Director of Public Prosecutions, accused the Prime Minister of disregarding the security service’s “serious reservations” about Lord Lebedev.
He added: “My thoughts in particular are with (the widow of poisoned Russian defector Alexander Litvinenko) Marina Litvinenko who knows first-hand the evils of Putin.
“Rather than stand in solidarity with her, the PM has forced her to witness him giving a peerage to someone who suggested her husband could have been murdered by MI6.”
Earlier this week Mr Johnson denied intervening to override security concerns about the peerage granted to Lord Lebedev, telling reporters: “That is simply incorrect… It suits Putin’s agenda to try to characterise this as a struggle between the West and Russia.”
Lord Lebedev, who owns British newspapers The Independent and the Evening Standard, has also dismissed allegations that he is an “agent of Russia” over claims a security services assessment saying the media mogul posed a national security risk was withdrawn after Mr Johnson intervened.
In response to allegations which surfaced last week that he had been identified as a national security risk before the PM had the assessment withdrawn, he acknowledged that his father had been a KGB officer but it was “a long time ago”.
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In a statement which was published on the Evening Standard website, Lord Lebedev said: “At the moment many with Russian roots are under scrutiny, including myself.
“I understand the reason for this as it is inevitable when events of such magnitude occur and the world order as we have known it in recent decades suddenly gets torn up.
“But I am not a security risk to this country, which I love. My father a long time ago was a foreign intelligence agent of the KGB, but I am not some agent of Russia.
“I may have a Russian name but that makes me no less a committed or proud British citizen than anyone else in this country of ours.
“Being Russian does not automatically make one an enemy of the state, and it is crucial we do not descend into Russiaphobia, like any other phobia, bigotry or discrimination.”
The Moscow-born media mogul has long held ties to the British establishment. In addition to the Prime Minister, Lord Lededev has long-standing friendships with A-list celebrities in the UK.